This is News Plus Special English. I'm Marc Cavigli in Beijing.
For villagers on Yan-shan Mountain, 300 kilometers from Beijing, ecological improvement has led to better growing conditions, cleaner spring water and fresher air, but wild animals have emerged as a new menace.
In Long-hua County in the city of Cheng-de, Hebei Province, hordes of boars are often seen digging corn seeds for food on farmland during the spring, and eating corn and potatoes in the autumn, leaving villagers with scant harvests.
In one extreme case, male boars were found to have mated with domesticated pigs raised on the mountain, which later gave birth to a litter of more than a dozen hybrid piglets.
The hybrid animals have long mouths, red-yellow fur with black and white stripes. They are too restless to be kept in a pigsty.
Xiao Fan, a forestry engineer with the county's forestry bureau, says he once saw a horde of around 20 boars wandering the mountain. The animals looked smart and vigilant with adults surrounding the piglets inside the horde.
More than 100 boars are estimated to live around several villages in Lan-qi Township alone. Wild boars were rarely seen in the township ten years ago.
Harming wild boars is illegal. To protect their crops, villagers set off fireworks and beat on iron basins to try to scare them away.
Boars are not the only threat to emerge amid the area's ecological improvement. Over the past two to three years, wild leopards and Siberian tigers have been confirmed to have eaten sheep and cows in mountainous areas in Hebei and Heilongjiang provinces in northeast China.
According to Chinese law, the local government should compensate victims for relevant losses caused by wild animals. However, as most local governments have no compensation standards or specific budget allocation for the damage, enforcement has been poor.